OpenSource means the SourceCode to the software is available.
It often refers to Software released under the GNU or a similar license, and thus overlaps with the "FreeSoftware" term. However, the two should not be confused, as OpenSource software may be non-Free, even non-free. Examples include commercial versions of Unix or Java, of which the SourceCode is available, but third parties are not allowed to distribute it.
DebianLinux has a "nonfree" section for software that the project may legally distribute but which does not meet the project's definition of FreeSoftware. This includes many OpenSource programs.
Compare Free and FreeSoftware.
124 pages link to OpenSource:
